So, I’m trying to code a train simulation, where my train ( composed of locomotives and wagons) moves on a railway, but I’m struggling with motion ( or movement?) handling. The code is too long to be put here all at once, but I will provide the function that moves the trains :

function moveTrains(contexte, matrice, plateau) {
    let trains = get_trains(plateau); //gets us a list of the available trains on the board
    let plateau_init = new Plateau();
    cree_plateau_initial(plateau_init); // i made this variable to keep track of the old board before the trains were put, so when the trains move away, i can restore the spot to where it was
    

    for (let train of trains) {
        let x = train.x;
        let y = train.y;
        let direction = Direction.right; //it shouldn't be right always, but for now this isn't the problem
        let nouvelle_position = direction.avancer(x, y); //avancer is the french for move forward, it just updates the coordinates according to the direction
        let avant = Direction.gauche.avancer(x,y); //gauche is left, which means i'm trying to go back to the previous box or spot
        let avant_x = avant.x;
        let avant_y= avant.y;
        let nouvelle_case_x = nouvelle_position.x; // new position coordinates
        let nouvelle_case_y = nouvelle_position.y;
        console.log(plateau.cases[x][y]); //debug

        if (
            nouvelle_case_x >= 0 && nouvelle_case_x < LARGEUR_PLATEAU &&
            nouvelle_case_y >= 0 && nouvelle_case_y < HAUTEUR_PLATEAU &&
            plateau.cases[nouvelle_case_x][nouvelle_case_y] !== Type_de_case.Foret 
        ) { //  console.log(plateau.cases[avant_x][avant_y]);
             // here starts the problem
            if (plateau.cases[avant_x][avant_y] != Type_de_case.wagon) //if the previous box is not a wagon we free it, putting whatever original rail was there
            AjouterObjet(plateau, x, y, plateau_init.cases[x][y]); //ajouterobjet is  a function that adds objects
            AjouterObjet(plateau, nouvelle_case_x, nouvelle_case_y, plateau.cases[x][y]); //we update the next spot by advancing our locomotive or wagon
            plateau.cases[nouvelle_case_x][nouvelle_case_y] = train.type; //update the type pf the box

           
            train.x = nouvelle_case_x;
            train.y = nouvelle_case_y;
        } else {
            
        }
    }

   
    dessine_plateau(contexte, plateau); //just to draw everything

when I start the simulation, the train moves on click but the trains in older positions don’t get erased, so it just keep on duplicating, i tried handling this recursively by moving each unit individually but there is always a problem.